The present invention relates to a monitoring device for an elevator, which device includes at least one contactlessly actuatable switching device.
In elevator installations, individual actions, for example travel of an elevator, are in general monitored with the assistance of switching devices. Several such switching devices must have a specific state in order to be able to undertake the proposed action. In particular, in the case of an elevator installation it must be ensured that before the start and during the travel of the elevator car all doors remain closed and mechanically locked.
There is known from the European patent document EP 0 535 205 B1 a monitoring device for a control device which comprises a safety chain and which is provided with a switching device comprising a sensor and able to be triggered in contactless manner. The switches or sensors are actuated by approach or movement away of a magnet.
The fact that the switch or the sensor reacts to each magnet independently of whether this magnet is the correct magnet intended for the selected switch or sensor is disadvantageous in this solution. The approach of an appropriate material is sufficient to trigger a valid signal. As soon as the switch is disposed in the working range of the magnet, it triggers a valid signal. A faulty function (false triggering) of the switch or the sensor can hardly be excluded without considerable cost. Erroneous triggering can also be caused by, for example, articles and/or external interferences, which put at risk the safe operation of the elevator installation.
The present invention has the object of proposing a monitoring device for a elevator of the kind stated in the introduction, which does not have the aforesaid disadvantages and which enables reliable monitoring free of disturbance. Moreover, the monitoring device is insensitive with respect to articles and external manipulations. The components to be monitored are unambiguously identifiable by means of the monitoring device.
One advantage is that a valid signal can be triggered only by, for example, a globally unique passive unit. The active unit cannot generate a valid signal without having the correct passive unit in range. A further advantage consists in that the monitoring is guaranteed by elements able to be produced economically.
A further advantage is that several switching devices can be monitored simultaneously with respect to functional capability and state. The interlinking of several active units takes place in the manner that the responses of all passive units are so linked that a mutual influencing in the sense of a false interpretation can be excluded.
The fact that a data exchange between active and passive unit can take place only through proximity of the coils operating as antennae is of further advantage.
Moreover, it is advantageous that the passive unit does not need an energy supply or battery. This is achieved by the fact that it comprises an energy store in which the energy transmitted by the active unit can be stored. Energy is thus saved. As the energy for generation of the response has to be transferred, spontaneous activity is not possible.
All explained features are usable not only in the respectively stated combination, but also in other combinations or by themselves without departing from the scope of the invention.